UPDATE 1-Warm sea water in Finland reduces power from Loviisa nuclear plant

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(Adds comments from Fortum and regulator, background)

By Lefteris Karagiannopoulos

OSLO, July 25 (Reuters) - Finland’s Loviisa power plant, consisting of two reactors with a combined capacity of 1 gigawatt, had to reduce power by 170 megawatts on Wednesday as the sea water that is used to cool the reactors had become too warm, operator Fortum said.

Because of the very warm temperatures the Nordic region is currently experiencing, the sea water that is collected to cool the Loviisa reactors is warmer and the water released is also warmer, at 32 degrees Celsius on Wednesday.

Releasing hot water back to the sea after cooling the reactors could be a hazard and if it exceeds 34 degrees Fortum said the reactors must be shut down due to regulations.

“We decreased power by 170 megawatts for a bit less than two hours. The sea water that cools the reactors was at 24 degrees, which is warmer than usual,” Fortum’s chief of operations in the plant, Timo Eurasto, told Reuters.

Such a rare occurrence may happen again in the next days because of the unusually warm temperatures, he said, adding that there was no danger to people, the plant, or the environment.

“High sea water temperature may indeed reduce the efficiency of the cooling systems of the plant. This is compensated by reducing or shutting down the reactor power,” said Nina Lahtinen, nuclear safety section head at Finland’s regulator STUK.

In Germany traders warned last week that higher temperatures in August may create cooling issues for the country’s reactors, with E.ON subsidiary PreussenElektra cutting output slightly from two units.

Sweden’s nuclear energy regulator SSM, told Reuters on Tuesday that power production at the Forsmark nuclear plant has also been reduced “by a few percentage points” due to cooling issues.

Last time Fortum had to reduce power in its reactors due to warmer-than-usual cooling water was seven years ago, said Loviisa plant’s Eurasto.

Unusually warm and dry weather in the Nordics led temperatures to record highs this summer, affecting water levels at the reservoirs that feed Norway and Sweden with hydropower, causing prices to spike as a result. (Editing by Kirsten Donovan and Elaine Hardcastle)